organic chemistry and hydrocarbons - by razi
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Chapter 14
Organic Chemistry
ANDHYDROCARBONS
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Organic Chemistry -Introduction Organic chemistry is the study of carbon
compounds.
Animals, plants, and other forms of lifeconsist of organic compounds.
Nucleic acids, proteins, fats, carbohydrates,enzymes, vitamins, and hormones are all
organic compounds.
Biochemistry was developed later as thestudy of the chemical compounds and
reactions in living cells.Intro
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Organic Chemistry -Introduction Scientists had originally thought that organic
compounds contained a vital force due to
their natural origin. This was disproved by Friedrich Whler in 1828.
Whler was able to make urea, a carbon
compound in human urine, in the laboratory
from a mineral. Organic chemistry is an enormous field.
In this chapter we will investigate some of the
fundamental concepts.Intro
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Bonding in OrganicCompounds Besides carbon, the most common elements
in organic compounds are hydrogen, oxygen,
nitrogen, sulfur, and the halogens.
All of the preceding elements are non-metals,
therefore organic compounds have covalent
bonding.
Any structural formula that obeys the bonding
rules in the following table probablyrepresents a possible compound.
A drawn structure that breaks the bonding rules is
unlikely to exist.
Section 14.1
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Common Elements inOrganic CompoundsApplication of the octet ruleindicates that these elementsshould bond as shown below:
Section 14.1
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Identifying Valid & IncorrectStructural FormulasAn Example
Two structural formulas are shown above.Which on does not represent a real compound?
In structure (a) each H and halogen has onebond, each C has four bonds, and each O hastwo bonds.
This is a valid structure.
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Identifying Valid & IncorrectStructural FormulasAn Example
As we examine (b), we note that each H hasone bond, each C has four bonds, the N has
three bonds, BUT the O has three bonds. The O should only have two bonds.
Therefore (b) is not a valid structure.
Section 14.1
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Structural FormulasConfidence Exercise
The structural formula above appears in a
recent chemistry book. Check the number ofbonds to each atom and determine whether
any bonding rules are violated.
Section 14.1
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Identifying IncorrectStructural FormulasConfidence Exercise
This is not a valid
structure for caffeine!
O should havetwo bonds, C
should have 4
bonds
Each N should
have 3 bonds
Each Cshould have 4
bonds
Section 14.1
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Hydrocarbons Hydrocarbons are the most simple organic
compounds.
Hydrocarbons contain only carbon (C) andhydrogen. (H)
For classification purposes, all other organiccompounds are considered derivatives of
hydrocarbons. Hydrocarbons can be divided into aromatic and
aliphatic hydrocarbons.
Section 14.2
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Classification ofHydrocarbons
Section 14.2
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Aromatic Hydrocarbons Aromatic hydrocarbons contain one or
more benzene ring.
Benzene (C6H6) is the most importantaromatic hydrocarbon.
It is a clear, colorless liquid with a
distinct odor, and is a carcinogen(cancer-causing agent.)
Traditional Lewis Structure
Section 14.2
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BenzeneStructural Formulas andShort-hand Symbols The Lewis structure and the Kekul symbol both
indicate that the carbons in the ring have alternating
double and single bonds.
Section 14.2
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Other AromaticHydrocarbons Toluene is used in modeling glue. Naphthalene is use
in mothballs, and Phenanthrene are used in the
synthesis of dyes, explosives, and drugs.
Section 14.2
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Benzene representation Benzene representation
howing a flat molecule withsix delocalized electronsforming an cloud above
and below the plane of thering.
Properties of the benzenemolecule and advancedbonding theory indicate
this structure. Thesix electrons appear to beshared by all the carbonatoms in the ring.
Section 14.2
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Substituted for the Hs in theBenzene RingA vast array of other compoundscan be produced
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Drawing Structures forBenzene DerivativesAn Example Draw the structural formula for 1,3-
dibromobenzene.
First, Draw a benzene ring.
Section 14.2
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raw ng ruc ures orBenzene DerivativesAn Example (cont.)
Second, attach a bromine atom (bromo)
to the carbon atom at the ring position
you choose to be number 1.
Section 14.2
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Drawing Structures forBenzene DerivativesAn Example (cont.)
Third, attach a second (di) bromine atom to
ring position 3 (you may number either
clockwise or counterclockwise from carbon 1)and you have the answer.
1,3-dibromobenzene
Section 14.2
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Structures for BenzeneDerivativesConfidence Exercise Which of the models below most
accurately represents the hydrogen
cyanide molecule, HCN?
From Ebbing/Gammon 7th Ed., p. 380
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DerivativesConfidence Exercise(cont.) C in (b) only has three bonds. C in (c) only has two bonds & N only has one.
C in (d) only has three bonds & N only hastwo.
Therefore, (a) appears to be the mostaccurate representation of the hydrogencyanide molecule, HCN.
N has three bonds, C has four bonds, H has one
From Ebbing/Gammon 7th
Ed., p. 380
Section 14.2
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Drawing Structures forBenzene DerivativesConfidence Exercise Draw the structural formula for 1-chloro-2-
fluorobenzene.
1. Draw a benzene ring.
3. Attach a fluorine atom to
ring position 2 and you
have the answer.
1-chloro-2-fluorobenzene
Section 14.2
Cl
F
2. Attach a chlorine atom (chloro) to the carbon atom at
the ring position you choose to be number 1.
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Aliphatic Hydrocarbons Aliphatic hydrocarbons are hydrocarbons
having no benzene rings.
Aliphatic hydrocarbons can be dividedinto four major divisions:
Alkanes
Cycloalkanes
Alkenes
Alkynes
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Classification ofHydrocarbons
Section 14.3
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Alkanes Alkanes are hydrocarbons that contain only
single bonds.
Alkanes are said to be saturated hydrocarbons Because their hydrogen content is at a maximum.
Alkane general formula CnH2n + 2 The names of alkanes all end in -ane.
Methane butane are gases Pentane C17H36 are liquids
C18H38 and higher are solids
Section 14.3
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theAlkane SeriesAll satisfy the general formulaCnH2n+ 2
Section 14.3
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Visualization of anAlkanes Structure
Section 14.3
Structural formula a graphicalrepresentation of the way atomsare connected
Condensed structural formula
save time/space and areconvenient
Ball-and-Stick models 3D
models that can be built bystudents
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Models of Three Alkanes
Names, Structural Formulas, Condensed StructuralFormulas, and Ball-and-Stick Models
Section 14.3
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Methane TetrahedralGeometryBall-and-
Stick &
Space-
FillingModels
Carbons
four single
bonds form
angles of
109.5o
Section 14.3
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Alkanes Energy RelatedProducts Methane = primary component of natural
gas
Propane & Butane = primary componentof bottled gas
Gasoline = pentane to decane
Kerosene = alkanes with n = 10 to 16 Alkanes with n > 16 diesel fuel, fuel
oil, petroleum jelly, paraffin wax,lubricating oil, and asphalt
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Alkane Products Alkanes are also found in paints, plastics,
drugs, detergents, insecticides, and cosmetics.
Only 6% of the petroleum consumed goes into
making these products. The remaining 94% of the petroleum is burned
as one of the various energy-related products.
Although alkanes are highly combustible, they
are otherwise not very reactive.
Any reaction would require the breaking of the
strong CH and CC bonds.
Section 14.3
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Alkyl Group Alkyl group contains one less hydrogen
than the corresponding alkane.
In naming this group the -ane isdropped and -yl is added.
For example, methane becomes methyl.
Ethane becomes ethyl.
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This group does not existindependently but occurs bondedto another atom or molecule.
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Constitutional Isomers Compounds that have the same molecular
formula but different structural formulas
In the case of many alkanes there is more thanone way to arrange the atoms
For example butane and isobutane
Both of these alkanes have the molecular
formula of C4H10
But their structural formula and arrangement is
quite different
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ButaneContinuous-Chain or Straight-Chain StructureC4H10B
a
l
l
-a
n
d
-S
t
i
c
kSection 14.3
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Isobutane (2-methylpropane)Branched-chain Structure
C4H10B
a
l
l
-a
n
d
-S
t
i
c
k Section 14.3
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Constitutional Isomers Constitutional Isomers may exist
whenever it is possible to construct a
different structural arrangement: Using the same number and types of atoms
Without violating the octet rule
In other words, the same atoms may beconnected to one another in different, but
valid, ways.
Section 14.3
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Number of PossibleIsomers of Alkanes Carbon Atoms
can bond in
many different
ways
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Organic CompoundNomenclature Due to the large number, variety, and
complexity of organic compounds, a
consistent method of nomenclature hasbeen developed.
Section 14.3
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ys em oNomenclatureFor Alkanes Compound is named as a derivative of the
longest continuous chain of C atoms.
Positions & names of the substituents added
If necessary, substituents named alphabetically More than one of same type substituent di, tri, tetra
The C atoms on the main chain are numbered
by counting from the end of the chain nearest
the substituents.
Each substituent must have a number.
Section 14.3
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An Example to Consider The longest continuous chain of C atoms is five
Therefore this compound is a pentane
derivative with an attached methyl group
Start numbering from end nearest the substituent The methyl group is in the #2 position
The compounds name is 2-methylpentane.
Section 14.3
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Substituents in OrganicCompounds
Section 14.3
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w u uNameAn Example
Draw the structural formula for2,3-dimethylhexane.
Note that the end name is hexane .
Draw a continuous chain of six carbon(C) atoms, with four bonds around each.
Section 14.3
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raw ng a ruc ure rom aNameAn Example (cont.)
Number the C atoms from right to left.
Attach a methyl group (CH3--) to carbon
number 2 and number 3.
Add necessary H atoms.
2,3-dimethylhexane
Section 14.3
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raw ng a ruc ure rom aNameConfidence Exercise
Draw the structural formula for
2,2,4-trimethylpentane.
Note that the end name ispentane .
Draw a continuous chain of five carbon
(C) atoms, with four bonds around each.
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a NameConfidence Exercise(cont.)
Number the C atoms from right to left.
Attach two methyl groups (CH3--) to carbon
number 2 and one to number 4.
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Drawing a Structure from aNameConfidence Exercise (cont.)
Add necessary H atoms. 2,2,4-trimethylpentane
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2,2,4-trimethylpentaneBall-and-Stick Model
Copyright Bobby H. Bammel. All rights reserved.
Section 14.3
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Cycloalkanes Members of the cycloalkane group
possess rings of carbon atoms.
They have the general formula CnH2n.
Each carbon atom is bonded to a total of
four carbon or hydrogen atoms.
The smallest possible ring consists of
cyclopropane, C3H6.
Section 14.3
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The First FourCycloalkanes
Note that in the condensed structural formulas, there is a
carbon atom at each corner and enough hydrogens are
assumed to be attached to give a total of four single bonds.
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Drawing the Structure of aCycloalkane Draw the geometric figure indicated by
the compounds name , pentane.
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Drawing the Structure of aCycloalkane Place each substituent on the ring in the
numbered position 1 chloro-2-ethyl-
1-chloro-2-ethylcyclopentane
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Alkenes Members of the alkene group have a double
bond between two carbon atoms.
One hydrogen atom has been removed fromtwo adjacent carbon atoms, thereby allowingthe two adjacent carbon atoms to form adouble bond.
General formula is CnH2n Begins with ethene (ethylene)
C2H4
Section 14.3
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Some Members of theAlkene Series
Section 14.3
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Naming Alkenes -anesuffix for the corresponding alkane is
changed to -enefor alkenes.
A number preceding the name indicates the C
atom on which the double bond starts. The carbons are numbered such that the double
bond has the lowest number.
For example, 1-butene and 2-butene
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Alkenes are very Reactiveand are termedunsaturatedhydrocarbons Alkenes will characteristically react with hydrogen to
form the corresponding alkane.
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Alkynes Members of the alkyne group have a triple
bond between two carbon atoms.
Two hydrogen atoms have been removed
from each of two adjacent carbon atoms,
thereby allowing the two adjacent carbonatoms to form a triple bond.
General formula is CnH2n-2
Begins with ethyne (acetylene) C2H2
Section 14.3
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Some Members of theAlkyne Series
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Alkynes are UnsaturatedHydrocarbons Due to the triple carbon bond, each alkyne molecule
can react with two molecules of hydrogen.
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Derivatives ofHydrocarbons Organic molecule characteristics depend on
the number, arrangement, and type of atoms.
Functional Group any atom, group of atoms,or organization of bonds that determine
specific properties of a molecule
Generally the functional group is the reactive part of
the molecule. Due to the functional groups presence, certain
predictable properties ensue.
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Derivatives ofHydrocarbons Examples of functional groups include:
The double bond in alkenes & triple bond in
alkynes.
Cl atom, F atom,OH group, methyl (CH3)
group.
Derivatives of hydrocarbons are organic
compounds that contain atoms other thanC and H.
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Alkyl Halides Alkyl halides have the general formula RX,
where X is a halogen and R is an alkyl group
CFCs (chlorofluorocarbons) are examples of
alkyl halides.
A well known CFC is dichlorodifluoromethane
(Freon-12)
Extensively used in the past in cooling devices.
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Alkyl Halides Another example of an alkyl halide is
chloroform. In the past it was used as a surgical anesthetic but
it is now a known carcenogen.
Carbon tetrachloride was also usedextensively in the past, until it was linked toliver damage.
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IsomersAn Example
Draw the structural formulas for the two alkylhalide isomers that have the molecular formulaC
2
H4
Cl2
.
Recall that C atoms form four bonds, H & Clform one bond each.
Draw a two-carbon backbone.
Add enough bonds so that each C has four.
Section 14.4 Drawing Constitutional
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IsomersAn Example (cont.) Note, there are just enough open bonds to attach thefour H and two Cl atoms. Fill in the Cl atoms in as many ways as possible.
Remember that you are constrained by the tetrahedralgeometry (109.5o) of the four C bonds.
Fill in the open bonds
with H atoms and name
the compounds.
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IsomersConfidence Exercise
Two constitutional isomers of C3H7F exist.Draw the structure for each.
Note that the formula ratio is that of an alkane.
Draw a three-carbon backbone. Add enough bonds so that each C has four.
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IsomersConfidence Exercise (cont.)
Note, there are just enough open bonds toattach the seven H and the one F atoms.
Fill in the F atoms in as many ways as
possible.
Remember that you are constrained by thetetrahedral geometry (109.5o) of the four Cbonds.
Section 14.4 raw ng ons u ona
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IsomersConfidence Exercise (cont.)
Fill in the open bonds with H atoms andname the compounds.
1-Fluoropropane 2-Fluoropropane
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Alcohols
Alcohols are organic compounds containingthe hydroxyl group, OH, attached to an
alkyl group.
General formula is ROH
Their IUPAC (International Union of Pure andApplied Chemistry) names end in -ol.
The most simple alcohol is methanol
Also called methyl alcohol or wood alcohol.
(poisonous)
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Alcohols
Another common alcohol is ethanol.(CH3CH2OH)
Also known as ethyl alcohol or grain alcohol
Least toxic and most important of the alcohols
Ethanol is used in alcoholic beverages,perfumes, dyes, and varnishes.
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Other Alcohol Examples Rubbing alcohol is
another alcohol
example.
Also known as 2-
hydroxypropane or
isopropyl alcohol
Ethylene glycol is an
alcohol used widely asan antifreeze and
coolant.
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Carbohydrates Compounds that contain multiple
hydroxyl groups in their molecularstructure.
Names end in -ose
Sugars, starches, and cellulose are themost important carbohydrates.
Glucose (C6H12O6) and fructose(C6H12O6) are important sugars.
Note that glucose and fructose are isomers.
Section 14.4 Structures of Glucose,
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Fructose,and Sucrose Glucose &
Fructose bond
together to formSucrose + H2O
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Carbohydrates - Sugars Fructose is the sweetest of all sugars and
is found in fruits and honey.
Glucose (also called dextrose) is found insweet fruits, such as grapes and figs, in
flowers, and in honey.
Carbohydrates must be broken down intoglucose for circulation in the blood.
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Carbohydrates - Starch Starch consists of very long chains (up to
3000 units) of glucose.
Produced by plants in their seeds, tubers,and fruits
When these plants parts are eaten, our
digestive processes covert the starchesback into glucose.
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Carbohydrates - Cellulose Cellulose is also a polymer of glucose and has
the general formula (C6H10O5)n. Slightly different structure with different properties
than starches Cell walls of plants are dominantly composed
of cellulose.
Humans do not have the appropriate enzymes
(called cellulases) to break cellulose down. Termites and many herbivores contain bacteria
that allow the breakdown of cellulose.
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Amines Organic compounds that contain nitrogen and
are basic (alkaline) are called amines.
General formula for an amine is RNH2.
One or two additional alkyl groups could be
attached to the N atom, in place of H atoms. Amine examples include methylamine,
dimethylamine, and trimethylamine.
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Amines Strong Odors
Most simple amines have strong odors. The odor given off by raw fish is due to an
amine that it contains.
Two particularly foul smelling amines are
formed by decaying flesh.
Cadaverine (1,5-diaminopentane)
Putresine (1,4-diaminobutane)
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Amines - Medicinal
Many amines have medicinal applications. Amphetamines raise the glucose level in the
blood resulting in less fatigue and hunger.
These synthetic drugs certainly have legitimate
medical uses, but can be addictive and lead toinsomnia, excessive weight loss, and paranoia.
Benzedrine is one type of amphetamine.
Section 14.4 The French artist David
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portrays The Death ofSocrates due to the deadlyalkaloid coniine
Section 14.4
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Carboxylic Acids Carboxylic acids contain the carboxyl
group . (COOH)
They have the general formula RCOOH.
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Carboxylic Acids Formic acid is the simplest
carboxylic acid.
This is the substance that
causes the painful sting ofinsect bites.
Vinegar is a 5% solution of
acetic acid.
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Esters Ester a compound that has
the following general formulaRCOOR
In the general formula for an ester the R andR can be any alkyl group. Although R and R can be identical, they are usually
different.
Contrary to amines, most esters have pleasantodors. Many flowers and ripe fruits have fragrances and
tastes due to one or more esters.
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Natural flavors are generallycomplex mixtures of esters andother constituents
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Formation of an Ester Ester formation the reaction of a carboxylic acid
and an alcohol give an ester and water
Heat is required and sulfuric acid is a catalyst.
Note, in this reaction that theOH from the carboxylicacid unites with the H from the alcohol to form H2O.
The remaining two fragments bond together to form theester.
Section 14.4 Writing an Equation for
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Ester FormationAn Example Complete the equation for the sulfuric
acid-catalyzed reaction between acetic
acid and ethanol.
Section 14.4 Writing an Equation for
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Ester FormationAn Example (cont.) Lasso theOH from the acetic acid and the H
from the ethanol to form H2O.
Attach the remaining acid and alcohol
fragments together forming ethyl acetate.
Section 14.4 y ce a e o ecu e
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An ester used as a solvent inlacquers and other protectivecoatings
Insert figure 14.17, p.386, 11/e
From Ebbing, General Chemistry, 6th Ed. Section 14.4
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Fats Fats are a type of ester formed by the
combination of the trialcohol named
glycerol and fatty acids. Glycerol is CH2(OH)CH(OH)CH2(OH)
Stearic Acid (C17H35COOH) is found in beef
fat, and is a typical fatty acid.
Section 14.4
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Fats Generally fats from animals are solid at
room temperature.
Fats from plants and fish are generallyliquid at room temperature.
Liquid fats are referred to as oils.
Section 14.4
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Hydrogenation Liquid fats contain double bonds between
some of the carbon atoms.
These liquids fats are termed unsaturated.
Hydrogenation is the process of adding H to
the C atoms that have a double bond.
The hydrocarbon chains become saturated or nearly
saturated and the liquid fat is changed to a solid.
A common example of hydrogenation is the
reaction cottonseed oil to margarine.
Section 14.4 y rogena on
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When Cottonseed Oil (liquid) ishydrogenated, Margarine (solid) isthe result.
Section 14.4
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Soaps Soap the sodium slats of fatty acids
Soap is formed by reacting a fat with
sodium hydroxide (NaOH, lye.) The ester bonds break giving rise to
glycerol and sodium salts of the fatty
acids. Sodium stearate is a typical soap.
Section 14.4
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Soap Like Dissolves Like Generally we want to dissolve stains made by
nonpolar compounds such as grease.
The polar end of the soap dissolves in water. The other end of the soap molecule is long and
nonpolar.
This nonpolar end dissolves in the grease.
The emulsified grease droplets can be rinsed away.
Section 14.4 The long nonpolar chains
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of the detergent moleculedissolve the grease.
Section 14.4
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Amides Amides are nitrogen-containing organic
compounds with the general formula
RCONHR.
Section 14.4
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Amide Formation Amide formation is similar to ester formation.
A carboxylic acid reacts with an amine to form
water and an amide, as shown below.
Section 14.4 Writing an Equation for
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Amide FormationAn Example Complete the equation for the reaction to
form Phenacetin.
Section 14.4 r ng an qua on or
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Amide FormationAn Example (cont.)
Lasso theOH from the acid and the H fromthe amine to form H2O.
Attach the remaining acid and amine fragments
together forming Phenacetin.
Section 14.4
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Amino Acid Amino acids are organic compounds that
contain both an amino and carboxyl group.
Glycine and alanine are the simplest amino
acids. Proteins are extremely long polyamides,
formed by the condensation of amino acids. Proteins can range from a few thousand formula
units (insulin) to several million formula units. Proteins serve as both structural components and
enzymes.
Section 14.4
Linking Amino Acid
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Molecules Glycine and alanine react to form water and
another amino acid. This process can be repeated, eventually forming a
protein.
Section 14.4 and their
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DerivativesNames andGeneralFormulas
Section 14.4
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Synthetics Attempts to duplicate nature have long been a
goal of chemists.
Basic formulas and structures became known
as the science of chemistry progressed. As attempts were made to synthesize natural
compounds, synthetic compounds werecreated.
Synthetics are materials whose moleculeshave no duplicate in nature.
Section 14.5
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Synthetic Polymers The first synthetic polymer was prepared by
Leo Baekeland in 1907.
Commercially this substance was used as an
electrical insulator, called Bakelite. Chemists soon discovered that only slight
substitutions to a molecule could create newsubstances with very different properties.
Knowing the chemical properties of the originalmolecules and the substitutes allowed chemists topredict the resulting properties.
Section 14.5
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Synthetic Polymers Due to the scientific approach, chemists
were able to tailor new molecules for
specific purposes.
Plastics are probably the best known of
this group of synthetic polymers.
They can be molded and hardened formany different purposes.
Section 14.5
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Synthetic Polymers A polymer is a compound of very high
formula mass whose long chain
molecules are made of repeating units.
Monomer is the fundamental repeating
unit of a polymer.
There are two major types of polymers:Addition polymers
Condensation polymers
Section 14.5
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Addition Polymers Addition polymers are formed when molecules
of an alkene monomer add to one another.
Recall that alkenes have a double bond
between two carbon atoms. Under the proper reaction conditions the
double bond opens up and attaches itself bysingle bonds to two other monomer molecules.
Each of these monomers will then in turnattach to another monomer, and so on andon
Section 14.5
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Polymerization of Ethene
The subscripted n on polyethyleneindicates that the unit shown in bracketsis repeated thousands of times.
Polyethylene is the simplest of the
synthetic polymers. It is significantly inert chemically and is
used to make containers.
Section 14.5
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Teflon Teflon is made by the polymerization of
tetrafluoroethene.
This polymer is a hard, strong, chemicallyresistant compound with a high melting
point and very low surface friction.
Section 14.5 Drawing the Structure of
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an Addition Polymer - AnExample An addition polymer can be prepared from
vinylidene chloride, CH2==CCl2. Draw the
structure of the polymer.
To form the polymer the double bonds of all themonomers (CH2==CCl2) must open up and
repeatedly bond to the growing chain of
monomers.
The structure is shown as:
Section 14.5
Common
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AdditionPolymers
Section 14.5
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Condensation Polymers Condensation polymers are formed from
molecules of two or more reactive
groups.
Water is the other product, hence the name
condensation polymers.
Polyethylene terephthalate (PET) is
formed from the polymerization of
tetephthalic acid and ethylene glycol.
Section 14.5
Nylon A Condensation
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Polymer
Nylon was first introduced to the public in1939 at the New York Worlds Fair.
Nylon is formed from the polymerization of
adipic acid and hexamethylenediamine.
Section 14.5
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Velcro Velcro is a popular fastener made of
nylon.
The hooks of one surface entangle theloops of the other surface.
Section 14.5
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